Optical receiver, optical transmission system, and span-loss monitoring method

Abstract

An optical receiver includes a converter configured to convert, into an electrical signal, an optical signal including error correction information, the optical signal being received from a transmitting side; a corrector configured to correct an error on the electrical signal, based on the error correction information; a threshold controller configured to control a threshold value discriminating a power of the electrical signal, based on a result of the error correction; a table configured to form therein data of a relationship between the threshold value and a power of an optical noise occurring when the optical signal is amplified within an optical transmission path; and a deriving unit configured to obtain the power of the optical noise corresponding to the threshold value from the table.

What is claimed is: 
     
       1. An optical receiver comprising:
 a converter configured to convert, into an electrical signal, an optical signal including error correction information, the optical signal being received from a transmitting side; 
 a corrector configured to correct an error on the electrical signal, based on the error correction information; 
 a threshold controller configured to control a threshold value discriminating a power of the electrical signal, based on a result of the error correction; 
 a table configured to form therein data of a relationship between the threshold value and a power of an optical noise occurring when the optical signal is amplified within an optical transmission path between the transmitting side and the optical receiver; 
 a deriving unit configured to obtain the power of the optical noise corresponding to the threshold value from the table; 
 a gain controller configured to control a gain of the amplification based on a span loss in the optical transmission path; 
 a pump light generator configured to generate pump light injected into the optical transmission path; and 
 a pump light controller configured to control a transmission power of the pump light based on the gain of the amplification. 
 
     
     
       2. The optical receiver according to  claim 1 , wherein
 data of a relationship between the threshold value and a power ratio of an optical noise to an optical signal is stored in the table, and 
 the deriving unit finds the power ratio corresponding to the threshold value from the table, and obtains a power of an optical noise, based on the power ratio and a reception power of the optical signal. 
 
     
     
       3. The optical receiver according to  claim 2 , wherein the data formed in the table is preliminarily obtained based on an experiment at a time of design of the optical receiver. 
     
     
       4. The optical receiver according to  claim 1 , wherein the deriving unit calculates the span loss in the optical transmission path, based on the transmission power of the optical signal notified from the transmitting side, a reception power of the optical signal, the power of the optical noise, and the gain of the amplification. 
     
     
       5. The optical receiver according to  claim 4 , wherein the data formed in the table is preliminarily obtained based on an experiment at a time of design of the optical receiver. 
     
     
       6. The optical receiver according to  claim 1 , wherein the data formed in the table is preliminarily obtained based on an experiment at a time of design of the optical receiver. 
     
     
       7. The optical receiver according to  claim 1 , wherein the data formed in the table is preliminarily obtained based on an experiment at a time of design of the optical receiver. 
     
     
       8. The optical receiver according to  claim 1 , wherein the data formed in the table is created, at a time of initial optical communication of the optical receiver, by waveforms of the optical signal corresponding to the transmission power of the pump light injected into the optical transmission path controlled by the pump light controller while disconnection and restoration of the optical signal are repeated. 
     
     
       9. An optical transmission system comprising:
 an optical transmitter configured to transmit an optical signal including error correction information; and 
 an optical receiver configured to receive the optical signal, the optical receiver including
 a converter configured to convert the received optical signal into an electrical signal; 
 a corrector configured to correct an error on the electrical signal, based on the error correction information; 
 a threshold controller configured to control a threshold value discriminating a power of the electrical signal, based on a result of the error correction; 
 a table configured to form therein data of a relationship between the threshold value and a power of an optical noise occurring when the optical signal is amplified within an optical transmission path between the optical transmitter and the optical receiver; 
 a deriving unit configured to obtain the power of the optical noise corresponding to the threshold value from the table; 
 a gain controller configured to control a gain of the amplification based on a span loss in the optical transmission path; 
 a pump light generator configured to generate pump light injected into the optical transmission path; and 
 a pump light controller configured to control a transmission power of the pump light based on the gain of the amplification. 
 
 
     
     
       10. The optical transmission system according to  claim 9 , wherein
 data of a relationship between the threshold value and a power ratio of an optical noise to an optical signal is stored in the table, and 
 the deriving unit finds the power ratio corresponding to the threshold value from the table, and obtains a power of an optical noise, based on the power ratio and a reception power of the optical signal. 
 
     
     
       11. The optical transmission system according to  claim 9 , wherein the deriving unit calculates the span loss in the optical transmission path, based on the transmission power of the optical signal notified from the optical transmitter, a reception power of the optical signal, the power of the optical noise, and the gain of the amplification. 
     
     
       12. A span-loss monitoring method comprising:
 receiving an optical signal including error correction information from a transmitting side; 
 converting the optical signal into an electrical signal; 
 correcting an error on the electrical signal, based on the error correction information; 
 controlling a threshold value discriminating a power of the electrical signal, based on a result of the error correction; 
 obtaining a power of an optical noise corresponding to the threshold value from a table in which data of a relationship between the threshold value and a power of an optical noise occurring when the optical signal is amplified within an optical transmission path formed between the transmitting side and an optical receiver; 
 controlling a gain of the amplification based on a span loss in the optical transmission path; 
 generating pump light injected into the optical transmission path; and 
 controlling a transmission power of the pump light based on the gain of the amplification. 
 
     
     
       13. The span-loss monitoring method according to  claim 12 , wherein
 data of a relationship between the threshold value and a power ratio of an optical noise to an optical signal is stored in the table, 
 the power ratio corresponding to the threshold value is found in the table, and 
 a power of an optical noise is obtained based on the power ratio and a reception power of the optical signal. 
 
     
     
       14. The span-loss monitoring method according to  claim 12 , further comprising:
 calculating the span loss in the optical transmission path, based on the transmission power of the optical signal notified from the transmitting side, a reception power of the optical signal, the power of the optical noise, and the gain of the amplification.